Studies will be continued on the mechanisms whereby chromosome imbalance results in abnormalities of development and function. The research goals for the coming year are: a) The quantitation of gene dosage effects for H-2 in embryos aneuploid for chromosome 17. b) The formation of chimeras with trisomy 17 cells to determine if trisomic cells are viable and, if so, to obtain trisomic splenocytes and thymocytes for analysis of H-2 and Tla. c) The formation of chimeras with monosomy 1, 12, 17, and 19 cells to determine whether these aneuploidies are cell lethals. d) The comparative study of protein synthesis of normal and aneuploid cell strains and tissues, including trisomy 17 in the mouse and trisomy 21 in Drosophila.